Harken Stand-Up Base Ball-Socket 3-1625 mm Low Load Base Swivel Stand up bases allow a wide variety of blocks to be held upright, swivel freely, or pivot so lines have a fairlead under load. The ball and socket design lets blocks articulate up to 45 degrees and swivel freely. The 460 and 461 bases (high load versions of the 010 and 029) have stainless steel reinforcement plates to handle the high load capacities of 57 mm and 75 mm Carbo blocks.